Electrical resistor and method of making same



April 8, 1947. s, oop 2,418,804

ELECTRICAL RESISTOR AND METHOD OF MAKING SAME Filed Oct. 8, 1945 gm, If HiHh IH i m INVEN TOR.

gang/1252M %0%W Lw5r% Patented Apr. 8, 1947 ELECTRICAL RESISTOR AND METHOD OF MAKING SAME Stanley R. Hood, Birmingham, Mich., assignor to Modern Metals and Materials, Chicago, Ill.

Application October 8, 1945, Serial No. 620,988 2 18 Claims.

My invention relates to electrical resistors of high ohmic value and to the method of producing the same.

In accordance with my present invention, electrical resistors having good mechanical strength, abrasion resistance and uniformity of linear electrical resistance are readily obtainable with resistances, for example, ranging from 1000 to 100,000 ohms per inch of developed length of resistor.

Resistances of high ohmic value have heretofore been produced but, in general, they are fragile and require vacuum sealing in their construction or they are of a character which prevents their being used in the same variable manner as conventional wire-wound resistors of lower ohmic ratings. Moreover, due to practical difficulties in producing wire of sufiiciently fine diameter, "it has frequently been found necessary to utilize non-metallic materials with resultant and concomitant disadvantages with which those versed in the art are familiar.

I have discovered that electrical resistors of unusually satisfactory characteristics may be produced by drawing a line or lines directly on glass or other insulating material, preferably of vitreous character, by means of a relatively sharp-edged or pointed piece of metallic titanium or titanium-base alloys. The lines thus produced are mechanically stable and do not smear. The nature of the bond between the glass and titanium line has not been fully ascertained. However, it is remarkably strong so that, for example, scraping with a sharp-edged razor blade has no appreciable effect in removing the line.

The nature of my invention may be explained in somewhat more detail in conjunction with 'the accompanying drawings wherein:

Fig. 1 shows an illustrative embodiment of a resistor made in accordance with my invention.

Fig. 2 is a plan viewof a schematic showing of one manner of producing resistors of the type with which my present invention deals.

Reverting to Fig. 1, numeral I0 designates a cylindrical glass rod, preferably of Pyrex glass and having a uniform diameter and a smooth or uniform peripheral surface which may, if desired, be produced by grinding and polishing or etching operations. Said surface bears a line H, in the form of a helix, and consisting of metallic titanium, said line having been marked or drawn on said glass rod, said line being of uniform width. Metallic terminals i2 and I3, of conventional construction, are pressed on the opposite ends of the rod l0, being applied after the line H has been drawn.

The production of a uniform line requires the maintenance of constant conditions, as, for example, the maintenance of a uniform surface for marking. the utilization of a constant pressure of the metallic titanium against the glass or the like, and the maintenance of the shape of the marking edge of the metallic titanium as the mark is being drawn. In Fig. 2, which illustrates, in schematic form, apparatus for accomplishing this result, numeral 14 represents a revolving chuck of a lathe head which holds the glass rod l6 upon which the titanium marking is to be placed. The titanium marking member is in the form of a circular disc ll which is supported on opposite faces by clamping plates l0 and 19. The disc I1 is mounted for rotation, preferably in the same direction of rotation of the glass rod l6, and, to this end, a sheave or pulley 2| is fixed on shaft 22 on which the marking disc 11 is supported, and is driven through belt 23 by means of motor 24. -It will be understood that the speed of rotation of the marking disc ll' may be adjusted, in relation to the speed of rotation of the glass rod [6, so as to provide the optimum contact time therebetween. The marking disc I! is held against the glass rod 16 at a constant or substantially constant pressure through spring or dead weight loading means 26, thereby automatically eliminating or offsetting eifects of eccentricity of the glass rod l6 or irregularities in its surface. A diamond or similar dressing tool 21 rides over the edge of the marking disc I! in order to assure a continually resized or uniform edge for presentation against the glass rod ii. The entire marking mechanism is mounted on a cross slide 28 which moves on a screw member 29 and is adapted to move longitudinally of the chuck at a rate of speed selected to produce the desired spacing between successive turns on the glass rod ii.

In certain cases, for example, where it is desired to reduce the length or number of turns of the metallic titanium in order to produce a change in resistance, a non-uniform metallic titanium line may be drawn on the glass rod by varying the marking conditions in such a manner as to accelerate the speed at which the glass rod [6 is rotated to change the lead or by gradually reducing or increasing the pressure exerted against the glass rod by the metallic titanium.

It is sometimes advantageous to lubricate the metallic titanium disc ll during the marking operations and, for this purpose, compounds such 3 as carbon tetrachloride, trichlcroethylene and the like may be played against said disc.

After the titanium markings have been applied to the glass rod, the same may be subjected to suitable heat treatment, it being understood that by proper control of time, temperature and atmosphere, the resistance may be modified to bring the resistors within certain desired, predetermined limits. I

In place of glass, other analogous non-conducting or insulating materials may be utilized as, for example, pcrcelains, marble, and various synthetics. I prefer to use vitreous materials and particularly glass. In general. for best results, the non-conducting material should be one which is harder than the metallic titanium so that it is not scratched thereby.

In the production of the markings on the glass, I prefer particularly to use pure or substantially pure metallic titanium. In the broader aspects of the invention titanium-base alloys may be used, that is, alloys containing a major proportion of titanium. High ohmic resistances may also be produced, in the manner described above, by utilizing metallic zirconium or zirconiumbase alloys instead of metallic titanium, but I prefer to utilize the latter as resistors produced therewith in the manner herein described are especially advantageous.

While perhaps in most instances resistors made in accordance with my invention will be of the type in which the metallic titanium or like line is of uniform or substantially uniform width and thickness, resistors may be made in which the width and thickness of the line vary so that there is a non-linear relation between line length and resistance. In a similar way, a flat surface or base of non-conducting materia1 may be marked with a spiral line so as to provide a non-linear relation of length to resistance.

The uses of such resistors as described herein are many. They may be employed, for example, in conjunction with electronic tube and potentiometer type circuits such as are used in industrial instruments or controls which function as a result of the interruption of a circuit or change in the resistance responding to a mechanical movement produced by a change in temperature, pressure, humidity, etc. An example of such a circuit is a burglar alarm system in which a titanium line is drawn around the edge of a plate glass window and the two ends connected to an electrical source, amplifier, and relay to operate an alarm should a break or crack in the window interrupt the current flow through the titanium. Other uses will readily suggest themselves to those versed in the art in the light of my teachings herein.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a method of making an electrical resistor, the steps which comprise drawing at least one line on a non-conductive surface with a relatively sharp-edged or pointed member selected from the group consisting of titanium and titanium-base alloys, and connecting the resulting line or lines to terminal members.

2. In a method of making an electrical resistor, the steps which comprise drawing a helix on a non-conductive base with a relatively sharpedged or pointed member selected from the group consisting of titanium and titanium-base alloys, and connecting the resulting markings to terminal members.

3. In a. method of making an electrical resistor, the steps which comprise drawing at least one line on a vitreous non-conductive surface with a relatively sharp-edged or pointed member selected from the group consisting of titanium and titanium-base alloys, and connecting the resultin line or lines. adjacent the ends thereof, to terminal members.

4. In a method of making an electrical resistor, the steps which comprise drawing a helix on a glass cylindrical rod with a relatively sharpedged or pointed member selected from the group consisting of titanium and titanium-base alloys, and connecting the resulting markings, adjacent the ends thereof, to terminal members.

5. In a method of making an electrical resistor, the steps which comprise rotating 9. cylindrical non-conductive rod about its axis, maintaining a relatively sharp-edged or pointed marking member, formed of a material selected from the group consisting of titanium and titaniumbase alloys, against the surface of the rotating rod under substantially uniform pressure and while maintaining a substantially uniform edge or point on said marking member whereby to draw a line of substantially uniform thickness on the cylindrical surface of said rod, and providing relative movement longitudinally of said rod between said rod and said marking member whereby said line is generated in the form of a helix.

6. In a method of making an electrical resistor, the steps which comprise rotating a cylindrical non-conductive rod about its axis, rotating a relatively sharp-edged disc about its axis, said disc being formed of a member selected from the group consisting of titanium and titanium-base alloys, maintaining the sharp edge of said disc against the surface of the rotating rod under substantially uniform pressure and while maintaining a substantially uniform edge on said disc, whereby to draw a line of substantially uniform thickness on the cylindrical surface of said rod, and providing relative movement longitudinally of said rod between said rod and said disc whereby said line is generated in the form of a helix.

7. In a method of making an electrical resistor, the steps which comprise rotating a, cylindrical, vitreous non-conductive rod about its axis, rotating a. relatively sharp-edged disc about its axis and in the same direction of rotation as that of the rod, said disc being formed of a member selected from the group consisting of titanium and titanium-base alloys, maintaining the sharp edge of said disc against the surface of the rotating rod under substantially uniform pressure and while maintaining a substantially uniform edge on said disc, whereby to draw a line of substantially uniform thickness on the cylindrical surface of said rod, providing relative movement longitudinally of said rod between said rod and said disc whereby said line is generated in the form of a, helix, and then connecting the resulting line, adjacent the ends thereof, to terminal members.

8. An electrical resistor comprising a cylindrical, vitreous non-conductive rod, a resistance medium comprising a line extending from approximately end to end of said base, said line being in the form of a helix and formed of a member selected from the group consisting of titanium and titanium-base alloys, and terminal members connecting said line at approximately the opposite ends thereof.

9. An electrical resistor comprising a non.

conductive base, a, resistance medium comprising a continuous line extending from approximately end to end of said base, said line being formed of a member selected from the group consisting of titanum and titanium-base alloys, and terminal members connecting said line at approximately the opposite ends thereof.

10. An electrical resistor comprising a cylindrical non-conductive base, a resistance medium comprising a line extending from approximately end to end of said base, said line being in the form of a helix and formed of a member selected from the group consisting of titanium and titanium-base alloys.

11. An electrical resistor comprising a nonconductive base, and a resistance medium comprising a. continuous line extending from approximately end to end of said base, said line being formed of a member selected from the group consisting of titanium and titanium-base alloys.

12. In a method of making an electrical resistor, the steps which comprise drawing at least one line on a non-conductive surface with a. relatively sharp-edged or pointed member selected from the group consisting of zirconium and zirconium-base alloys, and connecting the resulting line or lines to terminal members.

13. In a method of making an electrical resistor, the steps which comprise drawing a helix on a non-conductive base with a relatively sharpedged or pointed member selected from the group consisting of zirconium and zirconium-base alloys, and connecting the resulting markings to terminal members.

14. In a. method of making an electrical resistor. the steps which comprise drawing at least 16. An electrical resistor comprising a cylin-- drical, vitreous non-conductive rod, a resistance medium comprising a line extending from approximately end to end of said base, said line being in the form of a helix and formed of a member selected from the group consisting of zirconium and zirconium-base alloys.

17. An electrical resistor comprising a nonconductive base, and a resistance medium comprising a, continuous line extending from approximately end to end of said base, said line being formed of a member selected from the group consisting of zirconium and zirconium-base alloys.

18. An electrical resistor comprising a cylindrical glass rod, a resistance medium comprising a line extending from approximately end to end of said base, said line being in the form of a helix and formed of a member selected from the group consisting of zirconium and zirconium-base alloys, and terminal members connecting said line at approximately the opposite ends thereof.

STANLEY R. HOOD. 

